7.Intraoperative Complications

Question 1

What is are more likely to increase risks of complications in anaesthesia?

Answer 1

1. Patient factors - species (large, small, exotics more likely to have problem)
2. Breed
3. Weight extremes
4. Age Extremes
5. Procedure factors e.g. haemorrhage

Question 2

What systems are the systems most affected by anaesthesia? which do we need to ensure stay stable?

Answer 2

•	CNS
•	Cardiovascular
•	Respiratory
Need to ensure above stay stable is we want recovery
•	Renal 
•	Hepatic

Question 3

What are the MOST common complications under anaesthetic?

Answer 3

3 Hs
– Hypotension (low BP), most common
– Hypothermia
– Hypoventilation (hypercapnia, hypoxaemia)

Question 4

What is Systemic Vascular Resistance?

Answer 4

how constricted or dilated blood vessels are

Question 5

Blood pressure =

CO =

Answer 5

Cardiac Output (CO) x Systemic Vascular Resistance (SVR)

– CO = Heart rate (HR) x Stroke Volume (SV)

Question 6

What number do we need out mean arterial pressure to be over? Why?
What is the best measurement to look at for this?

Answer 6

Over 60 mmHg to maintain organ perfusion.

BLOOD PRESSURE

Question 7

How do we assess BP during anaesthesia?

Answer 7

by measuring 3 things:

• Systolic arterial pressure = GREATER than 60mmHg
• Diastolic
• Mean arterial pressure most interested in MUST BE MAINTAINED ABOVE 60 mmHG

Question 8

Caused of Hypotension udner anaesthesia

Answer 8

Reduced CO

Reduced systemic vascular resistance

Question 9

Reduced CO can be due to what….

Answer 9

Reduced stroke volume (volume heart pumping out LV during each systolic contraction)
• Hypovolaemia/dehydration
• Reduced venous return – e.g. due to being in dorsal recumbency (squashes blood vessels), IPPV (inc pressure in chest
• Disease – pericardial effusion (heart surrounded by fluid)

OR
Reduced heart rate
• Drugs (alpha 2 agonists)
• Disease – e.g 3rd Degree AV block

Question 10

Issue with inhalation agents

Answer 10

Because Vasodilation
Drugs (in particular volatile agents such as isoflurone and seroflurone = vasodilation = reduced BP)
= reduces Systemic vascular resistance

Question 11

How to treat HYPOtension… step by step

Answer 11

CPHFDPS
Read notes
1. Cuff
2. Plane
3. HR
4. Fluids
5. Drugs
6. Position
7. Stop ventilating

Question 12

Consequences of hypotension

Answer 12

• Organ/tissue damage  not enough blood supply to organs
– Acute kidney injury
– Myopathy (particularly in horses, can even be fatal)
– Severe hypotension
– Poor perfusion of heart
• Arrhythmias
• Death

Question 13

What is hypothermia defined as?

How common?

Answer 13

Temperature less than 37

It is the next most intraoperative complication after hypotension

Question 14

Caused hypothermia

How to prevent

Answer 14

cavity allows room temp air into 37 deg place)
• Reduced heat production (still)
• Abolished behavioural responses (shiver, find shelter)
• Alterations in hypothalamic function due to drugs

Prevent:
• Take care to avoid burns
• Pre-operative warming (as soon as give premed give blanket!)
• Blankets
• Bubble wrap around extremities
• Incubator
• Warm air
• Heated mats
• Heat and moisture exchanger (HME) – maintains normal resp heat and moisture so stopping it being lost as animal breathes out.
N.B Most effective if started before anaesthesia

Question 15

Consequences of hypothermia

Answer 15

• Severe: Cardiovascular and haematological
– Arrhythmias  can be fatal
– Coagulopathies (colder platelets don’t function properly)
– Reduced immune function  post op infection
• Metabolic
– Reduced drug metabolism (enzymes work more slowly)  prolonged effects and delayed recoveries. Not what we want with anaesthesia!
– Shivering massively increases O2 demand and very unpleasant!

Question 16

Hypoventilation
How common?
What can it lead to?

Answer 16

• Very common under anaesthesia
• Can lead to 2 things
– Hypercapnia (increased blood content of CO2)
• Body is metabolising oxygen and glucose  CO2 and water
• CO2 should be taken to the lungs and breathed out.
• If not then builds up in blood stream, causing various problems
– Hypoxaemia (reduced blood content of O2)

Question 17

Causes of hypoventilation?

Answer 17

•	Effects of drugs on
–	CNS
•	Depress respiratory centre in brain = less likely to take breath
–	Respiratory muscles
•	relaxation
•	Positional changes
–	Dorsal vs sternal recumbency
•	Dorsal – intestines on diaphragm squashing lungs

Question 18

What is hypercapnia
What monitors it?
What is normal
What is hypercapnic?

Answer 18

Inc level CO2 in blood
Monitored by arterial blood pressure (PaCO2) and capnograph (ETCO2)
Normal =
CO2 35-45 mmHg
Hypercapnia if greater than 45 mmHg however only treat if 60mmHg!

Question 19

What causes hypercapnia?

Answer 19

•	Animal not ventilating as efficiently as before – not as frequently or not deep enough breaths
•	Hypoventilation  Main cause
•	Breathing systems
–	Non rebreathing, not enough FGF
–	Rebreathing, exhausted soda lime

Question 20

How do we treat hypercapnia?

Answer 20

• Increase minute ventilation (MV) – resp rate and tidal volume (how often breathing and how big each is)
– MV = RR (respiratory rate) x TV (tidal volume)

1) Lighten plane of anaesthesia
– Reduce vaporiser setting (VAA cause hypoventilation)
– Reduce rate of drug administration (opioids and other drugs cause hypoventilation too)
If can’t reduce plane of anaesthesia any further as patient is already light enough then..
2) Mechanical ventilation (giving breaths yourself
– Squeezing reservoir bag
– Intermittent Positive Pressure Ventilation (IPPV)